Gas turbine engines generally include combustion sections receiving fuel from a fuel manifold assembly coupled to a plurality of fuel nozzles. The fuel manifold assembly may experience high amplitude dynamics (e.g., pressure oscillations, vibrations, harmonics) under various engine operating conditions due to a flow or pressure of the fuel through the fuel manifold assembly, pressure oscillations from the combustion section, and/or dynamics such as vibrations, noise, or harmonics from the engine in general. For example, engine operating conditions may include those defined by a landing/take-off cycle (LTO) for aviation engines or similar ranges for industrial, marine, auxiliary power unit, turboprop or turboshaft configurations. Engine operating conditions may include a generally lower power ignition/start-up and idle operation, a generally higher power take-off and climb condition, and other power conditions in between, such as cruise and approach. As an engine operates across these and other various operating conditions, fuel pressure and flow through the fuel manifold assembly to the combustion section varies, which may result in one or more resonance conditions that may disrupt fuel flow to the combustion section and adversely affect engine operation, up to and including loss of combustion. Un-mitigated fuel manifold assembly dynamics may also result in structural damage to the fuel manifold assembly.
Pressure oscillations generally occur in combustion sections of gas turbine engines resulting from the ignition of a fuel and air mixture within a combustion chamber. While nominal pressure oscillations are a byproduct of combustion, increased magnitudes of pressure oscillations may result from generally operating a combustion section at lean conditions, such as to reduce combustion emissions, or a coupling between unsteady heat release dynamics of the resulting flame/combustion, the overall acoustics of the combustion section, and transient fluid dynamics within the combustor. Pressure oscillations generally result in undesirable high-amplitude, self-sustaining pressure oscillations within the combustion section that may propagate to the fuel manifold assembly. These pressure oscillations may result in intense, single-frequency or multiple-frequency dominated acoustic waves that may propagate within the combustion section and to the fuel manifold assembly, thereby inducing vibrations in the fuel manifold assembly that may result in oscillations in a flow or pressure of fuel within the fuel manifold assembly. Oscillation of the fuel flow or pressure may propagate from the fuel manifold assembly to the fuel nozzles and aggravate pressure oscillations inside the combustion section. Low frequency acoustic waves, such as those that occur during engine startup and/or during a low power to idle operating condition, and/or higher frequency waves, which may occur at other operating conditions, may reduce operability margin of the engine, may increase external combustion noise, vibration, or harmonics, or induce loss of flame. Increased pressure oscillations may damage combustion sections or accelerate structural degradation of the combustion section, the fuel manifold assembly, or the engine in general, thereby resulting in engine failure or increased engine maintenance costs.
Therefore, there exists a need for a damping structure and method for fuel manifold assemblies to attenuate dynamics at the fuel manifold assembly that may mitigate losses in operability margin, increases in noise, vibration, or harmonics, or structural degradation of the fuel manifold, combustion section, or engine.